To reduce the emission of nitrogen oxides it is known with internal combustion, in particular in diesel engines, to provide exhaust gas recirculation so that a larger or smaller amount of exhaust gas is supplied in each case to the combustion process of the engine. In this connection, a high-pressure exhaust gas recirculation is known on the one hand and a low-pressure exhaust gas recirculation on the other hand.
With the high-pressure exhaust gas recirculation, hot exhaust gases with up to 400° C. are recirculated to the inlet side of the internal combustion engine. This results in the disadvantage that the air fed to the internal combustion process is greatly heated up and accordingly is only able to make available little oxygen to the internal combustion processes so that the power of the internal combustion engine that can be achieved remains correspondingly low.
With the low-pressure exhaust gas recirculation, the exhaust gases to be recirculated are extracted from the exhaust line at a greater distance from the engine and at correspondingly significantly reduced temperatures and, subject to intermixing with cooled combustion air, directed to the inlet side of the engine. If the efficiency of the engine is to be increased by an exhaust gas turbocharger now this is synonymous to having to compress the cool exhaust gas-air mixture from the compressor wheel of the turbocharger in its compressor stage before, as a rule after flowing through a charge air cooler, it flows into the combustion chambers of the engine. In this way, high performances of the combustion engine with little emission of nitrogen oxides are possible, but the compressor wheel is subjected to extraordinary loading since abrasively acting particles and corrosively acting components are carried along in the recirculated exhaust gas. These are in particular oil and water-containing condensates which because of dew point undershooting develop in the exhaust gas and can lead to cavitation. For this reason, the endeavour in general has been to avoid condensation of steams in the recirculated exhaust gas before the compressor stage of the turbocharger. For this purpose, elaborate measures for separating the steam carried along in the recirculated exhaust gas have been provided up to now.